21020121220 has 48 divisors (see below), whose sum is σ = 50657701248. Its totient is φ = 7176983040.

The previous prime is 21020121197. The next prime is 21020121229. The reversal of 21020121220 is 2212102012.

It is a happy number.

It is a super-2 number, since 2×21020121220² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21020121220.

It is not an unprimeable number, because it can be changed into a prime (21020121229) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 277762 + ... + 345241.

It is an arithmetic number, because the mean of its divisors is an integer number (1055368776).

Almost surely, 2^21020121220 is an apocalyptic number.

21020121220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21020121220 is an abundant number, since it is smaller than the sum of its proper divisors (29637580028).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21020121220 is a wasteful number, since it uses less digits than its factorization.

21020121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 623260 (or 623258 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21020121220 its reverse (2212102012), we get a palindrome (23232223232).

The spelling of 21020121220 in words is "twenty-one billion, twenty million, one hundred twenty-one thousand, two hundred twenty".